1. Field of the Invention
The present invention relates to a cable network, and more particularly, to a transmission apparatus and a transmission method for a subscriber network in a cable network and a transmission system using the same.
2. Related Art
Data over cable service interface specification (DOCSIS) defines a standard interface protocol for a cable modem. Recently, an advanced DOCSIS standard provides channel bonding, multicasting support function enhancement, or the like, for large-capacity, high-quality data transmission. With the progress of converging broadcasting and communication using Internet Protocol (IP)-based transmission, the DOCSIS standard has become an infrastructure capable of receiving multimedia transmission services by converging broadcasting and communication in a standard for a cable network.
In a hybrid fiber-coaxial (HFC) network, digital broadcasting services and communication services have been provided through separate channels by using separate devices. The digital broadcasting services are modulated into RF signals in a quadrature amplitude modulation (QAM) scheme by using a moving picture expert group 2-transport stream (MPEG2-TS)-based broadcasting stream and are then transmitted by using a broadcasting frequency. The communication services are provided by using a DOCSIS protocol between a CMTS positioned at a head end and subscriber devices.
Recently, the boundaries between the broadcasting services and the communication services are gradually becoming indistinct. Further, the digital broadcasting services using the HFC network will gradually be developed from a type using the existing MPEG-2 TS to a type using internet protocol packets.
In the HFC network, a set of subscriber devices receiving the same transmission signals is referred to as a cell. Generally, several hundred to several thousand subscriber devices are disposed in a single cell. However, in order to improve service quality and transmission rate per subscriber, the cell has been developed into a micro cell type that includes several tens of subscriber devices, which drastically reduces the number of subscribers included in a single cell.
With the introduction of the micro cell, maintaining the existing CMTS may be inefficient. The existing CMTS IS designed in consideration of the transmission of services to several hundred to several thousand subscriber devices, such that it is very complicated and expensive.
There is a need for a transmission apparatus and a transmission method for a subscriber network keeping pace with the development of IPs of the digital cable broadcasting services and the micro cell of the HFC network.